CBSE Class 10 Science Carbon and its Compounds MCQs Set 10

Science Objective Questions and Answers: Chapter 04 Carbon and its Compounds

Review structured MCQ sets for Class 10 Science Chapter 04 Carbon and its Compounds. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.

Download Chapter 04 Carbon and its Compounds MCQs with Answers

Navigate directly to the 50 objective questions for Chapter 04 Carbon and its Compounds using the digital viewer below. Each practice set includes verified answer keys, allowing students to instantly cross-check their work and identify areas requiring further revision.

This CBSE Class 10 Science page gives 35 multiple choice questions on Chapter 4, Carbon and Its Compounds, each with the correct answer, a step-by-step explanation and a short teacher's note. The set tests double and triple covalent bonds, fullerene and marsh gas, isomerism and homologous series, esterification and vinegar, and the use of detergents in hard water, with 7 assertion-reason questions at the end.

Multiple Choice Questions

Question 1: Which of the following will contain covalent double bond between its atoms?
(a) H2
(b) O2
(c) NaCl
(d) Cl2
Show Answer & Explanation

Answer: (b) O2

Explanation:
1. Each oxygen atom has six valence electrons and shares two with the other atom, so O=O has a double bond.
2. H2 and Cl2 have single bonds, and NaCl is ionic.

Teacher's Note:
1. Oxygen needs two electrons to complete its octet.
2. Nitrogen has a triple bond.

Question 2: Which of the following gases is called ‘marsh gas’?
(a) H2
(b) CH4
(c) C2H4
(d) C2H2
Show Answer & Explanation

Answer: (b) CH4

Explanation:
1. Methane is produced by the decay of plant matter in marshes.
2. That is why it is called marsh gas.

Teacher's Note:
1. Methane is also the main gas in biogas.
2. It is the simplest hydrocarbon.

Question 3: How many valence electrons are present in carbon?
(a) 2
(b) 3
(c) 4
(d) 5
Show Answer & Explanation

Answer: (c) 4

Explanation:
1. Carbon has atomic number 6 and electronic configuration 2, 4.
2. The outer shell has 4 electrons.

Teacher's Note:
1. Valence electrons are in the outermost shell.
2. This gives carbon its valency of 4.

Question 4: Which type of bond is present between carbon-carbon atoms in acetylene?
(a) Single covalent bond
(b) Double covalent bond
(c) Triple covalent bond
(d) Electrovalent bond
Show Answer & Explanation

Answer: (c) Triple covalent bond

Explanation:
1. Acetylene is ethyne, HC≡CH.
2. The two carbon atoms share three pairs of electrons.

Teacher's Note:
1. Acetylene is the common name of ethyne.
2. Alkyne means triple bond.

Question 5: The bond between two identical non-metallic atom has a pair of electron :
(a) unequally shared between two atoms.
(b) transferred completely from one atom to another.
(c) with identical spins.
(d) equally shared between them.
Show Answer & Explanation

Answer: (d) equally shared between them.

Explanation:
1. Two identical atoms attract the shared pair equally.
2. So the pair is equally shared, giving a non-polar covalent bond.

Teacher's Note:
1. Identical atoms have identical pull.
2. Transfer gives an ionic bond.

Question 6: How many number of carbon atoms are joined in a spherical molecule of Buckminsterfullerene?
(a) 30
(b) 60
(c) 90
(d) 120
Show Answer & Explanation

Answer: (b) 60

Explanation:
1. Buckminsterfullerene has the formula C60.
2. It is a football-shaped molecule of 60 carbon atoms.

Teacher's Note:
1. The number is in the formula C60.
2. It is named after Buckminster Fuller.

Question 7: Buckminsterfullerene is an allotropic form of
(a) phosphorus
(b) sulphur
(c) carbon
(d) tin
Show Answer & Explanation

Answer: (c) carbon

Explanation:
1. Buckminsterfullerene (C60) is a football-shaped molecule made of 60 carbon atoms.
2. It is the third crystalline allotrope of carbon besides diamond and graphite.

Teacher's Note:
1. Allotropes are different physical forms of the same element.
2. Fullerenes are named after Buckminster Fuller.

Question 8: What does isomerism explain?
(a) A difference in molecular formulae.
(b) A difference in molecular weights.
(c) A difference in chemical properties and structural formulae.
(d) A difference in molecular composition.
Show Answer & Explanation

Answer: (c) A difference in chemical properties and structural formulae.

Explanation:
1. Isomers have the same molecular formula but different structural formulae.
2. Their different structures give them different chemical properties.

Teacher's Note:
1. Same molecular formula, different structure.
2. Butane and isobutane are a standard pair.

Question 9: Which of the following does not belong to the same homologous series?
(a) CH4
(b) C2H6
(c) C3H8
(d) C4H8
Show Answer & Explanation

Answer: (d) C4H8

Explanation:
1. CH4, C2H6 and C3H8 fit CnH2n+2 (alkanes).
2. C4H8 fits CnH2n, so it is an alkene.

Teacher's Note:
1. Test each formula against the general formulae.
2. Alkanes: CnH2n+2.

Question 10: Which of the following statements is not correct?
(a) A common functional group is present in different members of a homologous series.
(b) Two consecutive members of a homologous series differ by a –CH3 group.
(c) The members of a homologous series can be represented by one general formula.
(d) Different members of a homologous series have similar chemical properties.
Show Answer & Explanation

Answer: (b) Two consecutive members of a homologous series differ by a –CH3 group.

Explanation:
1. Two consecutive members differ by a –CH2– group (14 u), not by –CH3.
2. The other statements are true.

Teacher's Note:
1. Check the CH2 difference.
2. Adjacent members differ by 14 u.

Question 11: The table shows six organic compounds A, B, C, D, E and F: A C7H16; B C8H16; C C4H6; D C6H10; E C5H10; F C9H20. Identify the correct statements.
(a) A and F are saturated hydrocarbons while all others are unsaturated hydrocarbons.
(b) C and D belong to a homologous series having general formula CnH2n.
(c) B and E are alkynes.
(d) All the compounds have same physical and chemical properties.
Show Answer & Explanation

Answer: (a) A and F are saturated hydrocarbons while all others are unsaturated hydrocarbons.

Explanation:
1. A and F fit CnH2n+2 (alkanes, saturated), while B, E (alkenes) and C, D (alkynes) are unsaturated.
2. C and D fit CnH2n−2, B and E are alkenes, and different series differ in properties.

Teacher's Note:
1. Sort the compounds by general formula.
2. Saturated means alkane.

Question 12: Which of the following is the correct order for the boiling points of the given alkanes?
(a) CH4 < CH3CH3 < CH3CH2CH3 < CH3CH2CH2CH3
(b) CH4 > CH3CH3 > CH3CH2CH3 > CH3CH2CH2CH3
(c) CH4 > CH3CH3 < CH3CH2CH3 > CH3CH2CH2CH3
(d) CH4 < CH3CH3 > CH3CH2CH3 > CH3CH2CH2CH3
Show Answer & Explanation

Answer: (a) CH4 < CH3CH3 < CH3CH2CH3 < CH3CH2CH2CH3

Explanation:
1. In a homologous series the boiling point rises as the molecular mass increases.
2. So methane has the lowest and butane the highest boiling point.

Teacher's Note:
1. More carbon atoms mean stronger attraction between molecules.
2. Gradation in physical properties.

Question 13: Which of the following properties is not true regarding organic compounds?
(a) They are generally covalent compounds.
(b) Show isomerism
(c) Compounds have high melting and boiling points.
(d) Generally insoluble in water.
Show Answer & Explanation

Answer: (c) Compounds have high melting and boiling points.

Explanation:
1. Organic compounds are covalent with weak forces between molecules, so they have low melting and boiling points.
2. The other statements are correct.

Teacher's Note:
1. Covalent compounds melt at low temperatures.
2. Most are insoluble in water.

Question 14: Propane, with the molecular formula C3H8 contains:
(a) 4 covalent bonds
(b) 10 covalent bonds
(c) 8 covalent bonds
(d) 15 covalent bonds
Show Answer & Explanation

Answer: (b) 10 covalent bonds

Explanation:
1. Propane has 8 C–H bonds and 2 C–C bonds.
2. The total is 10 covalent bonds.

Teacher's Note:
1. Bonds in an alkane = 3n + 1.
2. Draw and count.

Question 15: What is the formula of propanal?
(a) CH3CH2CHO
(b) CH3CH2CH2CHO
(c) CH3COCH2
(d) CH3CH2COCH2
Show Answer & Explanation

Answer: (a) CH3CH2CHO

Explanation:
1. ‘Prop’ means three carbon atoms and ‘-al’ means the aldehyde group –CHO.
2. So propanal is CH3CH2CHO.

Teacher's Note:
1. Count the carbon in –CHO too.
2. CH3CH2CH2CHO is butanal.

Question 16: The reaction CH2 = CH2 + H2 → CH3 – CH3 is :
(a) substitution reaction
(b) addition reaction
(c) rearrangement reaction
(d) elimination reaction
Show Answer & Explanation

Answer: (b) addition reaction

Explanation:
1. Hydrogen is added across the C=C double bond of ethene to give ethane.
2. This is an addition reaction (hydrogenation).

Teacher's Note:
1. Unsaturated compounds undergo addition.
2. A catalyst such as Ni is used.

Question 17: Saturated hydrocarbons burn with a blue flame when:
(a) oxygen supply is insufficient
(b) oxygen supply is sufficient
(c) never burns with a blue flame
(d) always burns with a yellow sooty flame.
Show Answer & Explanation

Answer: (b) oxygen supply is sufficient

Explanation:
1. With enough oxygen, saturated hydrocarbons burn completely and give a blue, non-sooty flame.
2. With too little oxygen they burn incompletely and give a yellow sooty flame.

Teacher's Note:
1. The flame colour depends on the oxygen supply.
2. A blue flame means complete combustion.

Question 18: Identify A in the following reaction: CH3–CH2–OH → (A) + H2O (hot, conc. H2SO4)
(a) Ethane
(b) Methane
(c) Ethene
(d) Ethyne
Show Answer & Explanation

Answer: (c) Ethene

Explanation:
1. Hot concentrated sulphuric acid dehydrates ethanol.
2. Removing H2O from C2H5OH gives ethene, C2H4.

Teacher's Note:
1. Dehydration means removal of water.
2. Ethanol has two carbons, so the product has two.

Question 19: Glacial acetic acid is –
(a) 100% acetic acid free of water
(b) solidified acetic acid
(c) gaseous acetic acid
(d) frozen acetic acid
Show Answer & Explanation

Answer: (a) 100% acetic acid free of water

Explanation:
1. Glacial acetic acid is pure ethanoic acid with no water.
2. It is called ‘glacial’ because pure acid freezes to ice-like crystals at about 290 K.

Teacher's Note:
1. Vinegar is only 5–8% acid.
2. Glacial means pure, water-free.

Question 20: Which compound represents the vinegar?
(a) HCOOH
(b) CH3CHO
(c) HCHO
(d) CH3COOH
Show Answer & Explanation

Answer: (d) CH3COOH

Explanation:
1. Vinegar is a dilute solution of ethanoic (acetic) acid, CH3COOH.
2. HCOOH is formic acid, CH3CHO is ethanal and HCHO is methanal.

Teacher's Note:
1. Vinegar contains 5–8% ethanoic acid.
2. Formic acid is in ant stings.

Question 21: A compound ‘X’ reacts with a compound ‘Y’, to produce a colourless and odourless gas. The gas turns lime water milky. When ‘X’ reacts with methanol in the presence of concentrated H2SO4, a sweet smelling substance is produced. The molecular formula of the compound ‘X’ is –
(a) C2H4O
(b) C2H4O2
(c) C2H6O
(d) C2H6O2
Show Answer & Explanation

Answer: (b) C2H4O2

Explanation:
1. A gas that turns lime water milky is CO2, released when an acid reacts with a carbonate or hydrogencarbonate.
2. X also forms an ester with methanol, so X is ethanoic acid, C2H4O2.

Teacher's Note:
1. Acid + carbonate gives CO2.
2. Acid + alcohol gives ester.

Question 22: Two organic compounds ‘A’ and ‘B’ react with sodium metal and both produce the same gas ‘X’, but with sodium hydrogen carbonate, only compound B reacts to give a gas ‘Y’. Identify ‘A’, ‘B’, ‘X’ and ‘Y’:
(a) A = Ethylene, B = Ethyl alcohol, X = Carbon dioxide, Y = Hydrogen
(b) A = Ethyl alcohol, B = Acetic acid, X = Hydrogen, Y = Carbon dioxide
(c) A = Methyl alcohol, B = Ethyl alcohol, X = Hydrogen, Y = Carbon dioxide
(d) A = Acetic acid, B = Formic acid, X = Carbon dioxide, Y = Hydrogen
Show Answer & Explanation

Answer: (b) A = Ethyl alcohol, B = Acetic acid, X = Hydrogen, Y = Carbon dioxide

Explanation:
1. Both an alcohol and an acid react with sodium to release hydrogen (X).
2. Only the acid (acetic acid) reacts with NaHCO3 to release carbon dioxide (Y).

Teacher's Note:
1. Sodium reacts with –OH and –COOH.
2. Only acids react with hydrogencarbonates.

Question 23: An organic compound 'P' with molecular formula C2H4O2 turns blue litmus to red and gives brisk effervescence with NaHCO3. Identify the compound
(a) Methanoic acid
(b) Ethanoic acid
(c) Propanol
(d) Butanoic acid
Show Answer & Explanation

Answer: (b) Ethanoic acid

Explanation:
1. Turning blue litmus red and giving CO2 with NaHCO3 shows a carboxylic acid.
2. With the formula C2H4O2, it is ethanoic acid (CH3COOH).

Teacher's Note:
1. Two carbon atoms means ethanoic acid.
2. Methanoic acid is CH2O2.

Question 24: In which of the following compounds, —OH is the functional group?
(a) Butanone
(b) Butanol
(c) Butanoic acid
(d) Butanal
Show Answer & Explanation

Answer: (b) Butanol

Explanation:
1. The suffix ‘-ol’ indicates an alcohol with the –OH group.
2. Butanone is a ketone, butanoic acid has –COOH and butanal has –CHO.

Teacher's Note:
1. Learn the suffixes: -ol, -al, -one, -oic acid.
2. –COOH contains an –OH but is not called alcohol.

Question 25: Which among the following reactions is known as esterification reaction?
(a) CH3COOH + NaHCO3 → CH3COONa + H2O + CO2
(b) CH3COOH + NaOH → CH3COONa + H2O
(c) C2H5OH + CH3COOH → CH3COOC2H5 + H2O (H+)
(d) CH3COOC2H5 + NaOH → CH3COONa + C2H5OH
Show Answer & Explanation

Answer: (c) C2H5OH + CH3COOH → CH3COOC2H5 + H2O (H+)

Explanation:
1. Esterification is the reaction of a carboxylic acid with an alcohol in the presence of an acid catalyst to form an ester and water.
2. Option (c) shows this reaction.

Teacher's Note:
1. Acid + alcohol gives ester.
2. The ester is the product, not the reactant.

Question 26: Detergents can lather well in –
(a) soft water
(b) hard water
(c) river water
(d) any one of the above
Show Answer & Explanation

Answer: (d) any one of the above

Explanation:
1. Detergents do not form insoluble scum with Ca2+ and Mg2+ ions.
2. So they lather in soft, hard and river water alike.

Teacher's Note:
1. Soaps fail in hard water; detergents do not.
2. Detergents are ammonium or sulphonate salts.

Question 27: A student is given equal amount of three samples of water with temporary hardness labelled as ‘A’, ‘B’ and ‘C’. He keeps the three samples at different temperatures – A at room temperature, B at 50 °C and C at 95 °C. Which sample will give maximum amount of lather when 10 mL of soap solution is added to each sample and shaken for equal time?
(a) A only
(b) Both A and B
(c) Both B and C
(d) C only
Show Answer & Explanation

Answer: (d) C only

Explanation:
1. Temporary hardness is due to bicarbonates of calcium and magnesium, which decompose on boiling.
2. At 95 °C the most hardness is removed, so C gives the most lather.

Teacher's Note:
1. Heating removes temporary hardness.
2. The higher the temperature, the more hardness is removed.

Question 28: Compound 'X' works well with hard water. It is used for making shampoos and products for cleaning clothes. Compound 'X' is not 100% biodegradable and causes water pollution. Compound 'Y' does not work well with hard water and it is 100% biodegradable and does not cause water pollution. Identify compound 'X'.
(a) Detergent
(b) Soap
(c) Washing soda
(d) Baking soda
Show Answer & Explanation

Answer: (a) Detergent

Explanation:
1. Detergents work in hard water and are often non-biodegradable, so X is a detergent.
2. Soaps form scum in hard water and are biodegradable, so Y is soap.

Teacher's Note:
1. Detergents are effective in hard water.
2. Soaps are biodegradable.

Assertion–Reason Questions

Question 29:
Assertion (A): Carbon has a tendency to form multiple bonds.
Reason (R): Carbon has small size.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Because carbon is small, its atoms can come close enough to share two or three pairs.
2. So R explains why carbon forms multiple bonds.

Teacher's Note:
1. Small size allows effective overlap.
2. Silicon rarely forms multiple bonds.

Question 30:
Assertion (A): Carbon forms ionic compounds.
Reason (R): It is because of its valency of 4.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (d) A is false, but R is true.

Explanation:
1. Carbon cannot lose or gain four electrons easily, so it forms covalent, not ionic, compounds; A is false.
2. Its valency is 4, so R is a true statement.

Teacher's Note:
1. Carbon shares electrons.
2. A false, R true is option (d).

Question 31:
Assertion (A): C6H12, C2H4, C4H8 are alkenes and have double bond.
Reason (R): C3H4 and C5H8 are alkynes and have triple bond.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Explanation:
1. Formulae of the type CnH2n are alkenes, and CnH2n−2 are alkynes, so both statements are true.
2. The second statement does not explain why the first set are alkenes.

Teacher's Note:
1. Check the general formula of each series.
2. Two true statements need not be related as cause and effect.

Question 32:
Assertion (A): Saturated hydrocarbons are chemically less reactive.
Reason (R): All the valencies of carbon atom are satisfied by single covalent bonds.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. In saturated hydrocarbons all four valencies of carbon are satisfied by strong single bonds.
2. So they do not readily add other atoms, and R explains A.

Teacher's Note:
1. Strong single bonds are hard to break.
2. Unsaturated compounds are more reactive.

Question 33:
Assertion (A): For welding purpose a mixture of oxygen and ethyne is used.
Reason (R): Ethyne when burnt in air gives smoky flame.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Explanation:
1. The oxy-ethyne flame is very hot and is used for welding, so A is true.
2. Ethyne does burn with a smoky flame in air, so R is true, but this is the reason air is not used, not why the oxy mixture is used.

Teacher's Note:
1. Burning in pure oxygen gives complete combustion.
2. A smoky flame is a sign of incomplete combustion.

Question 34:
Assertion (A): Esterification is a process in which a sweet smelling substance is produced.
Reason (R): When esters react with sodium hydroxide an alcohol and sodium salt of carboxylic acid are obtained.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Explanation:
1. Esters are sweet-smelling compounds formed from an acid and an alcohol, so A is true.
2. Saponification of esters is also true but it does not explain why esterification gives a sweet smell.

Teacher's Note:
1. Esterification gives esters with a fruity smell.
2. Saponification is the reverse reaction.

Question 35:
Assertion (A): In esterification reaction, carboxylic acid and alcohol reacts in the presence of acid to give ester.
Reason (R): Saponification is the reverse of esterification.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Explanation:
1. A carboxylic acid and an alcohol in the presence of an acid catalyst form an ester, so A is true.
2. R is also true, but it does not explain how an ester is formed.

Teacher's Note:
1. R names the reverse reaction only.
2. Saponification uses NaOH.

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Multiple Choice Questions (MCQs) for Class 10 Science Chapter 04 Carbon and its Compounds

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